1. Field of the Invention
The present invention relates to switching power supplies, and particularly to a DC-DC voltage converter with low power loss.
2. Description of Related Art
Direct current to direct current (DC-DC) voltage converters (voltage converter for short) based on a bridge switching circuit are widely used in various electronic devices, such as computers, mobile phones, etc. A traditional voltage converter utilizes one or more pull-up and pull-down network transistors composing the bridge switching circuit to produce an alternating current (AC) signal. The AC signal is then applied to a low pass filter including an inductor and a capacitor. The low pass filter passes the DC component of the AC signal to the output of the voltage converter to power on subsequent functional modules. Detailed structures and characteristics of the traditional voltage converter are introduced by Volkan Kursun et al., “High Input Voltage Step-down DC-DC Converters for Integration in A Low Voltage CMOS Process”, IEEE Proceedings of 2004 International Symposium on Quality of Electronic Design, pp. 517-521, San Jose, Calif., USA, 22-24 Mar. 2004.
A typical voltage converter will be described. The typical voltage converter includes a pulse width modulation (PWM) controller chip, a bridge switching circuit composed of one or more pull-up and pull-down network transistors, and a low pass filter. The PWM controller chip includes a plurality of predetermined pins to perform its basic functions, such as generating control signals to turn on and off the transistors of the bridge switching circuit. However, to satisfy multi-functions, such as over-current protection, additional pins are required for the PWM controller chip. The additional pins limit the miniaturization of the voltage converter and increase the cost for the packaging of the PWM controller chip.
Therefore, an improved voltage converter is needed to address the aforementioned deficiency and inadequacies.